The present invention is related to communications in a computer network and is more particularly related to signalling various events associated with non-blocking communications calls initiated by a task of a parallel job in a distributed parallel data processing system.
In a distributed parallel data processing system a communication mechanism is provided to allow users to communicate between different tasks of a parallel job. Typically to alleviate the effect of communication delays a user is allowed to overlap computation with communication by the use of nonblocking communication calls. When a nonblocking call is invoked, the user needs to know when the call in question has "completed". There are many reasons to know that a nonblocking call has completed--for instance the user may have to free up resources used in the non-blocking calls or the user may want to reuse buffers provided to the nonblocking call.
In order to permit a high degree of concurrency, a low-level application programming interface (LAPI), to be described, defines three types of events associated with nonblocking calls which indicate whether (1) resources of a message are available at origin (2) resources of a message are available at target and (3) a particular message has completed (as related to the origin and target) with respect to the requestor.
Various solutions have been proposed to recognize events associated with nonblocking communication calls. Most previous solutions (MPI is one example) require a distinct handle per message of the user. A distinct handle per message requires more storage and may also be less efficient because it requires the user to check on each of these individually. MPI attempts to alleviate this problem by providing "wait.sub.-- any" and "wait.sub.-- all". However these still require a handle per message and thus the implementation is also expected to be more complex.
Further, MPI has a notion of standard and synchronous messages in order to allow the user to specify the type of nonblocking behavior required. This makes the use of the API more cumbersome since it burdens the user to have to select a particular interface.